class anxin:
    a1 = 1  #公有，public
    _a2 = 1 #保护，protected
    __a3 = 1#私有，private

class Student:
    def __init__(self,age):
        self.__age = age

    @property
    def age(self):
        return self.__age
    @age.setter
    def age(self,new_age):
        self.__age = new_age

stu1 = Student(20)
print(stu1.age)
stu1.age = 30
print(stu1.age)











